Spiral Filaments Research Articles

Citrus psorosis virus: nucleotide sequencing of the coat protein gene and detection by hybridization and RT-PCR.

Citrus psorosis virus (CPV) is a multicomponent ssRNA virus with a coat protein of approximately 48 kDa. The viral genome is encapsidated in short and long particles that are readily separated by sucrose density-gradient centrifugation. CPV particles are spiral filaments that are referred to as spiroviruses (SV). A cDNA library of purified short particles from isolate CPV-4 was prepared in a Lambda vector and screened for expression of the coat protein gene (CPG) with a monoclonal antibody to the coat protein. Sequencing of immunopositive clones indicated a single ORF encoding a 49 kDa protein. This ORF, when expressed in E. coli, gave a protein identical in size and immunoreactivity to the CPV coat protein. A full-length clone of the CPG was transcribed and used in Northern hybridization assays to establish that short particle RNA of CPV is negative sense and contains the CPG. Moreover, the CPG was not found on RNA extracted from long particles or on the sedimentable dsRNA from CPV infected tissue. RT-PCR assays were developed for the amplification of a 600 bp fragment of CPG and for the complete CPG (1317 bp). The 600 bp fragment from a biologically and serologically different isolate, CPV-6, was cloned, sequenced and found to share 86% (nucleotide) and 96% (amino acid) identity with CPV-4. BLAST analysis of sequences from CPV-4 and CPV-6 detected no significant nucleic acid or protein similarity with any known viral sequences.

Electron plasma profiles from a cathode with an r2 potential variation

A simple one-dimensional model of Maxwellian injection into a cylindrical Penning–Malmberg trap is presented. This model is used to predict the radial density profile of an electron column produced by a biased cathode with an r2 potential variation. The column density n(r) is assumed to depend upon the cathode potential voltage Vk(r) and the self-consistent space-charge potential φ(r) as n(r)∝exp{e[φ(r)−Vk(r)]/T}. A one-parameter family of theoretical solutions describes the radial density profiles. The model’s predictions agree well with electron density profiles resulting from a spiral tungsten filament measured over a wide range in cathode voltages.

TGB A phase in a series of swallowtailed chiral liquid crystals

A homologous series of chiral materials, 1-butylpentyl (S)-2-{6-[4-(4'-alkoxyphenyl)- benzoyloxy]-2-naphthyl}propionates, BPmPBNP (m=6-16), derived from a chiral moiety, (S)-2-(6-hydroxy-2-naphthyl)propionic acid, in conjunction with a swallowtail group attached to the external side of the chiral centre, has been synthesized and their mesomorphic phases have been studied. There were two frustrated phases: a blue (BP) phase and a twist-grain- boundary (TGBA) phase found enantiotropically in all materials. It is worth noting that, depending on the nature of the terminal chain length, two types of filament textures were observed in the TGB A phase: a vermis (filament) texture and a spiral filament texture. The formation of the TGB A phase was rationalized as due to the steric effect caused by the swallowtail of the materials. All materials exhibited a wide temperature range of the SmA phase, but only three materials (m=12, 13 and 16) possessed a monotropic SmC* phase over a narrow temperature range, indicating that the swallowtailed materials inhibit the formation of a tilted smectic phase.

Spiral filaments ? The signature of singular points in a large delta spot

A large delta spot (active region NOAA 6891, October 23 – November 4, 1991) is analysed, and it is found that some spiral filaments across the spot can be regarded as signatures of a singular point entity (SPE) which lies near a separator of this complicated magnetic field region. Near such an entity, 86% of the flares in the region were produced, including two white-light flares, one of which, being the largest flare of the region, was accompanied by a powerful mass ejection. In an island delta spot, a SPE could be recognized very close to the usual U-shaped inversion lines. Together with the other characteristics (bright Hα emission, highly sheared magnetic field, umbra obscured by Hα, magnetic flux imbalance in the range 2∶1–3∶1), the SPE can help us to predict effectively the sites for great flares to occur (Zirin and Liggett, 1987).

Interaction of bovine brain tubulin with the 4(1H)-pyrizinone derivative IKP104, an antimitotic drug with a complex set of effects on the conformational stability of the tubulin molecule.

The ligands of tubulin have proved to be excellent probes for the conformation of the tubulin molecule. The most varied in their effects on tubulin are those ligands which are competitive or noncompetitive inhibitors of vinblastine binding. The 4(H)-pyrizinone derivative 2-(4-fluorophenyl)-1-(2-chloro- 3,5-dimethoxyphenyl)-3-methyl-6-phenyl-4(1H)-pyridinone [sequence: see text] (IKP104) is a novel antimitotic drug which inhibits microtubule assembly in vitro and in vivo and polymerizes tubulin into spiral filaments. Using a fluorescence assay, we found that IKP104 appears to bind to tubulin at two classes of site, differing in affinity. IKP104 also blocks formation of an intrachain cross-link in beta-tubulin, induced by N,N"-ethylenebis(iodoacetamide), linking Cys12 to either Cys201 or Cys211. IKP104 appears to belong to that group of tubulin ligands which includes vinblastine, maytansine, rhizoxin, phomopsin A, dolastatin 10, and halichondrin B. An unusual effect of IKP104 is that it greatly enhances the decay or apparent unfolding or opening of the tubulin molecule. The sulfhydryl titer of tubulin is doubled and the exposure of hydrophobic areas on the tubulin molecule is tripled by IKP104. These effects of IKP104 are counteracted by vinblastine, maytansine, and phomopsin A, suggesting that IKP104 may be competing with these other drugs for binding to tubulin. However, the effects are also counteracted by colchicine and podophyllotoxin, implying a more complex effect, namely, that IKP104 and colchicine, even when both are bound to tubulin, are competing for their effects on the same domain of tubulin. Surprisingly, when IKP104 is used in conjunction with colchicine, binding of colchicine to tubulin is strongly stabilized.(ABSTRACT TRUNCATED AT 250 WORDS)

Five types of colloblast in a cydippid ctenophore, Minictena luteola Carré and Carré: an ultrastructural study and cytological interpretation

Minictena luteola Carré and Carré is a recently described, small mediterranean ctenophore, with five types of colloblast. We have examined the morphology of the colloblasts at different stages of differentiation by electron microscopy. The five types differ in size and structure at all stages of differentiation. This is the first report of colloblast polymorphism in ctenophores. Two of the types found in M. luteola differ significantly from the generally accepted structure of colloblasts, in particular by the absence of refractive vesicles. Examination of the structure of the five types of colloblast during differentiation has given us a better idea of the nature and organization of the axial filament and the origin of the spheroidal body and its relationship with the nucleus. Our observations lead us to question the axonemal nature of the spiral filament.

Encephalitozoon infection in a still-born foal

A stud Clydesdale foal was still-born near full term. Macroscopic examination revealed a normal placenta, pulmonary atelectasis and faint white mottling of the kidneys. Microscopically there was severe lymphoplasmacytic interstitial nephritis. Numerous organisms resembling Encephalitozoon cuniculi were present in the affected kidneys. The organisms occurred in the areas of inflammation as well as in the renal glomeruli and intracellular cysts in the renal tubular epithelial cells and exhibited Gram positive staining. Ultrastructurally the organisms possessed a polar vacuole and a spiral filament typical of Microsporidia. The organisms were not detected in sections of the other organs examined.

Three-dimensional vortex with a spiral filament in a chemically active medium

A new technique, the self-completion technique, for obtaining 3D vortices with a predetermined configuration of the filament has been used in experiments with the B-Z reagent. The technique has made it possible to obtained a 3D autowave vortex with a spiral filament, which has the form of a stationary spiral, emitting waves inwards and outwards. In the course of time, the spiral shortens to give rise to a region inside it, which the waves move to the center and vanish there.

The Vortex-Filament Nature of Reverse Flow on the Verge of Rotating Stall

On the verge of rotating stall, very orderly reverse flow forms from the outlet of the rotor/impeller along the casing/shroud toward the inlet in axial/centrifugal compressors (Koch, 1970; Haupt, et al., 1987). The experiment on a centrifugal compressor reveals furthermore that the reverse flow is composed of stable spiral vortex filaments. Their vorticity can be transferred to the inlet tip vortex, known as prerotation. The behavior of these vortex filaments is examined based on the fundamental research work on rotating bodies available in the literature. This result shows that the vortex filaments are composed of Taylor’s vortex pairs, but with unequal vortex strengths within the pair. They form the transition range from a laminar to a turbulent three-dimensional boundary layer with a very steep tangential velocity profile. This profile is associated with the appearance of a toroidal ring vortex in the rotor/impeller, acting as a recirculatig secondary flow. It can be further shown from the analysis of the extensive literature that the orderly path of the reverse flow is enabled by the cessation of the leakage flow of the rotor tip clearance. The reason for this is that the growing tangential flow field extends beyond the rotor tip up to the close proximity of the endwall, so that the tip clearance is blocked.

Systematics of Onchocleidus Mueller, 1936 (Monogenea: Ancyrocephalidae): phylogenetic relationships, evolution, and host associations

The phylogeny of Onchocleidus Mueller, 1936 (sensu Wheeler and Beverley-Burton 1989) is analysed cladistically. The putative monophyly of the genus is supported by three synapomorphies: dextral vaginal opening, spiral filament encircling the penis, and dorsal hamuli with reduced deep roots. Haplocleidus Mueller, 1937 and Pterocleidus Mueller, 1937 are considered synonyms of Onchocleidus. The spiral filament, previously considered synapomorphic for the group comprising Onchocleidus and Aethycteron Suriano and Beverley-Burton, 1982, is reinterpreted as independently derived in both genera. An alternative hypothesis is presented for the relationship between Onchocleidus and Aethycteron, with the spiral filament and accessory piece of Aethycteron arising through transformation of an accessory piece similar to that found in Urocleidus Mueller, 1934. This implies a sister-group relationship between Aethycteron and Urocleidus, not between Aethycteron and Onchocleidus. The host associations of Onchocleidus, Aethycteron, and Urocleidus are discussed in light of this hypothesis. Onchocleidus is assumed to have originated and (or) radiated on centrarchids; species of Onchocleidus parasitizing Percichthyidae are not monophyletic and probably spread to percichthyids via ecological association. Rather than assume that Aethycteron spread to percids by ecological association with centrarchids, it appears that percids were host to a common ancestor of Aethycteron and Urocleidus, which later radiated, giving rise to the two genera. The occurrence of Urocleidus on centrarchids is attributed to ecological association with percids.

Homologous pairing and the formation of nascent synaptic intermediates between regions of duplex DNA by RecA protein.

The RecA protein from E. coli gains access to duplex DNA, by nucleation from a short single-stranded gap, to form a spiral nucleoprotein filament that is capable of interaction with homologous duplex DNA. The observations described here demonstrate that any part of the nucleoprotein filament, whether it contains single- or double-stranded DNA, is capable of pairing with homologous duplex DNA. Homologous contacts between regions of duplex DNA lead to an increase in the initial rate and final extent of joint molecule formation. The experiments indicate that pairing is facilitated by the formation of nascent synaptic intermediates between duplex DNA sequences. Using chimeric form I DNA, which is incapable of forming an inter-wound or plectonemic joint with the gapped DNA due to the presence of flanking heterologous sequences, we show that these duplex-duplex pairing reactions involve extensive underwinding of the double helix.

Multiple-contour-dynamic simulation of eddy scales in the plane shear layer

The method of contour dynamics (CD) is applied to several inviscid prototype flows typical of the motions found in the transition region of the free shear layer. Examples of the interaction between the fundamental streamwise-layer perturbation and its first subharmonic are presented that illustrate the events of pairing and tearing of two rolled-up cores and also the coalescence of three rolled-up cores. The present simulations of the temporally unstable two-dimensional layer, at effectively infinite Reynolds number, support the hypothesis that the dynamics of the large-scale roll-up is only weakly dependent on Reynolds number. However, we find fine-scale structure that is not apparent in previous simulations at moderate Reynolds number. Spiral filaments of rotational fluid wrap around the rolled-up vortex cores producing ‘spiky’ vorticity distributions together with the entanglement of large quantities of irrotational fluid into the layer. Simulations proceeded only until the first such event because we were unable to resolve the fine detail generated subsequently. The inclusion of prescribed vortex stretching parallel to the vortex lines is found to accelerate the initial roll-up and to enhance the production of spiral vortex filaments. In the fundamental-subharmonic interaction, vortex stretching slows but does not prevent pairing.

The dynamics of three-dimensional scroll waves in excitable media

We investigate the motion of the central filament of a scroll wave in excitable medium. We assume that two-dimensional spiral solutions are known and use these solutions to produce slowly varying scroll waves in three-dimensional space. Using standard ideas from perturbation theory (multiscale techniques) we find equations governing the motion of the central filament of the scroll and the twist of the scroll wave. These equations are specialized to the case of a circular filament with uniformly distributed twist, to determine the collapse or expansion and vertical drift of the spiral filament and to a helical filament with drift. The predictions of these equations are in good qualitative agreement with the numerical experiments.

Spiral superconducting NbTi filaments: electric field and critical current

As a first step to a better understanding of the voltage—current characteristics of fine filament multifilamentary composite superconductors, the electric field and critical current along a single spiral-shaped filament were studied. When the spiral superconducting filament was carrying constant current and placed in a magnetic field, the local critical current and electric field vary due to the change of the angle between the magnetic field and filament axis. A theory is presented which enables us to calculate the mean and local values of the electric field and critical current of spiral samples for arbitrary orientation between the magnetic field and spiral axis. The presented experimental results are in good agreement with this theory.

Star Formation in the Large Magellanic Cloud

Methods used in pattern recognition and cluster analysis are applied to investigate the spatial distribution of the star forming regions. The fractal dimension of these structures is deduced. The new 21 cm, radio continuum (1.4 GHz) and IRAS surveys reveal scale structures of 700 pc to 1500 pc being identical with the optically identified star forming sites. The morphological structures delineated by young stars reflect physical parameters which determine the star formation in this galaxy. The formation of spiral arm filaments is understandable by stochastic selfpropagating star formation processes.

Ancyrocephalids (Monogenea) from Morone spp. (Percichthyidae) in North America, including redescriptions of Onchocleidus mimus Mueller, 1936 and O. interruptus Mizelle, 1936

The ancyrocephalids (Monogenea) parasitizing the temperate basses (Percichthyidae) of North America are reviewed. Onchocleidus mimus Mueller, 1936 is redescribed from material found on the gills of Morone chrysops (white bass) taken in Ontario. Onchocleidus rogersi (Hanek and Fernando, 1972) Beverley-Burton, 1984 is declared a synonym of O. mimus. Onchocleidus interruptus Mizelle, 1936 is redescribed from paratype material (14 specimens) found on M. mississippiensis (yellow bass) taken in Illinois. Additional morphometric and morphologic data for O. chrysops (Mizelle and Klucka, 1953) Beverley-Burton, 1984 are provided. Cleidodiscus sp. of S. Tedla and C. H. Fernando and "Tetraonchinae" of C. J. Sindermann are considered to be referrable to the genus Onchocleidus sensu Beverley-Burton. Following a study of type specimens of Aristocleidus hastatus Mueller, 1936 from M. saxatilis (striped bass) taken in Florida, the genus and species are recognised as valid. However, there is need for a revision of the generic diagnosis when new material becomes available as the morphology of the male copulatory complex appears to be distinctive and of a "type" as yet undescribed. Urocleidus nactus Mayes and Johnson, 1975 found on M. americana (white perch) taken in coastal waters of North Carolina is transferred to Pterocleidus Mueller, 1937 as Pterocleidus nactus (Mayes and Johnson, 1975) n. comb. The possibility that ancyrocephalids found on M. americana taken in estuarine waters of the Hudson River by V. M. Liguori and identified as U. biramosus (Mueller, 1937) are conspecific with P. nactus is discussed. Ancyrocephalids possessing the spiral filament penis type occur almost exclusively on fishes of the Percoidae. Possible evolutionary pathways involving ancestral dactylogyridans (sensu Beverley-Burton) parasitizing estuarine Percichthyidae or freshwater Centrarchidae are presented with particular reference to the ancryrocephalids found on Morone spp.

An indium-free mount for GaAs substrate heating during molecular beam epitaxial growth

The substrate mounting system for a Varian GEN/II molecular beam epitaxy (MBE) system was modified to allow the growth of device quality GaAs and AlGaAs epitaxial layers on GaAs substrates without the use of indium bonding. The indium-free holders are compatible and interchangeable with the standard molybdenum blocks that use indium bonding. The wafer is heated by direct radiation from the unmodified spiral filaments with no intermediate absorbers or backside wafer coatings. A commercial pyrometer with a silicon detector was used to measure the absolute temperature. The silicon detector is sensitive to radiation from 0.8 to 1.1 μm, which is primarily above the band gap energy of GaAs at substrate temperatures above 550 °C. For photon energies above the band gap the spectral emittance of GaAs is nearly independent of the substrate doping, thickness, and temperature. With this pyrometer a maximum temperature difference of 3 °C was measured over the central two-thirds of a 2 in. diam semi-insulating GaAs wafer. In contrast, the maximum temperature difference on n+GaAs substrates was significantly larger (30 °C over the central two-thirds of the wafer) and showed the same pattern as the filament configuration. This large difference is explained by a simple model which takes into account the smaller thermal conductivity and larger total emittance of n+GaAs compared to undoped GaAs.

Contrasting roles of tau and microtubule-associated protein 2 in the vinblastine-induced aggregation of brain tubulin.

Two different proteins, tau and microtubule-associated protein 2 (MAP 2), are able to stimulate tubulin polymerization into microtubules in vitro, but it is not certain if both proteins act by the same mechanism. We have examined the effects of tau and MAP 2 on the vinblastine-induced polymerization of tubulin into spiral filaments. In the presence of tau, vinblastine induced extensive aggregation of tubulin as shown by a large increase in turbidity. The increase in turbidity was accompanied by the formation of large numbers of spirals composed of a filament 40-60 A in diameter. The rate and extent of this aggregation into spirals were dependent on the concentrations of tubulin, tau, and vinblastine. Unlike normal microtubule assembly, this type of aggregation was not inhibited by colchicine or podophyllotoxin. In contrast, MAP 2, even at high concentrations, was less effective than tau at promoting the vinblastine-induced increase in turbidity of tubulin. In fact, MAP 2 strongly inhibited the effect of tau. These results indicate that tau and MAP 2 interact differently with the tubulin molecule in the presence of vinblastine and suggest that the two proteins may play different roles in regulating or promoting microtubule assembly. Vinblastine may thus be a useful probe in analyzing the modes of interactions of tau and MAP 2 with tubulin.

Role of RecA protein spiral filaments in genetic recombination.

Physical and enzymatic studies on RecA protein from Escherichia coli provide the basis for a molecular model of general genetic recombination, a novel feature of which is the role attributed to spiral filaments of RecA protein.

Structure and Dynamics of Magellanic Type Galaxies

In continuation of former work (Feitzinger 1980) the morphological structure of 68 SB(s)m systems, greater than 2!5 on ESO/SRC survey plates, was investigated. Three morphological features should be mentioned: 1.Stellar bars located asymmetrically with respect to the disk are found in 70% of the cases; the displacement relative to the disk diameter is Λ = 0.1 − 0.35.2.The disk is populated in 45 % of the cases by chains of HII regions (spiral arm filaments).3.Though not very frequent nearly 25 % of the SBm systems have a dominating HII region near the outer periphery and predominantly near one end of the bar.